Robbjack ST-646-12-A Corner Radius End Mill 3/8 in 6 Flute

Product Description

The ROBBJACK ST-646-12-A is a single-end, center-cutting corner radius end mill engineered for demanding metal removal in ferrous and exotic workpiece materials. Machined from solid carbide and finished with an AlTiN (PVD) coating, it delivers the hardness and thermal resistance required for dry or semi-dry cutting at elevated speeds. The tool measures 3/8 inches in diameter with a 7/8-inch length of cut, a 2.5-inch overall length, and a 3/8-inch straight-cylindrical shank. Six flutes with a variable helix and variable index geometry reduce chatter and improve surface finish across a wide range of cutting conditions. Right-hand cut and right-hand flute direction are standard. This end mill is installed by CNC machinists and tool and die professionals in production and job shop environments.

The ST-646-12-A is suited for milling steel, stainless steel, cast iron, superalloys, and titanium - material codes P, M, K, and S. Its corner radius geometry (0.0050 to 0.0070 inches) protects cutting edges from chipping during side milling, slotting, and profiling passes where square-corner tools would break down prematurely. The close pitch and high helix style support aggressive feed rates while maintaining chip evacuation. The tool mounts into a standard toolholder and does not feature coolant-through capability, so external coolant or air blast is used as needed. It is part of the ROBBJACK ST-646 series, designed for standard-length reach applications.

Key Features

• Solid carbide construction with AlTiN PVD coating for heat and wear resistance in ferrous and exotic materials
• Six-flute, variable helix and variable index design reduces harmonic vibration and improves surface finish
• Corner radius of 0.0050 to 0.0070 inches extends edge life during profiling and side milling
• Center-cutting capability allows plunge entry without a pre-drilled pilot hole
• Right-hand cut, right-hand flute, high helix style with close pitch for high feed rates
• Straight-cylindrical shank compatible with standard collet and shrink-fit toolholders

Compatibility

Designed for use with standard toolholders accepting a 3/8-inch straight-cylindrical shank. Primary workpiece materials are steel, stainless steel, cast iron, superalloys, and titanium (material codes P, M, K, S). Part of the ROBBJACK ST-646 series for standard-length milling applications.

Installation Notes

Installation is performed by qualified CNC machinists or toolroom personnel. Ensure the machine spindle is fully stopped and the tool is seated to the correct gauge length before tightening the toolholder. Verify shank runout with a dial indicator after clamping, as the shank diameter tolerance is 0.0001 to 0.0002 inches. This tool does not support coolant-through delivery; direct external coolant or air blast at the cutting zone to manage chip evacuation and heat.